1. Field
One or more embodiments of the present invention relate generally to an apparatus, method and medium for displaying a stereo image, and more particularly to an apparatus, method and medium for displaying a stereo image, in which predetermined areas are set to a left image and a right image of a stereo image, and a vertical error and a rotation error of the left image and the right image are compensated for using a vector difference of polygons displayed in each area.
2. Description of the Related Art
Digital TV has emerged to fulfill consumer demand for improved picture quality. A digital TV provides improved picture quality, and uses a different screen aspect ratio, as compared with a conventional analog TV, thereby providing users with more vivid images.
The picture quality of an image is an important factor in a two-dimensional (hereinafter, referred to as 2D) image. Recently, consumer demand for three-dimensional (3D) stereo imaging has increased, such that research in the area of 3D stereo imaging has increased.
The techniques for viewing stereo images can be classified into a stereoscopy technique, in which a user cannot view a stereo image without wearing stereo glasses, or an autostereoscopy technique in which a user can view a stereo image without glasses. The stereoscopy technique includes a polarization operation and a time-division operation, while the autostereoscopy technique includes a parallax barrier operation and a lenticular operation.
Conventional 3D stereo image (hereinafter, referred to as stereo image) broadcasting systems have been developed in Japan, Europe, the U.S., and other countries, but the commercialization of these systems has been delayed mainly due to problems such as visual fatigue and the inconvenience to users of wearing stereo glasses.
Visual fatigue occurring from stereo image systems is typically caused by accommodation-convergence breakdown and crosstalk.
When a user views an object in the real world, accommodation and convergence are intrinsically linked. Accordingly, the user recognizes depth without feeling fatigue. However, when a user views a stereo image through a conventional stereo image system, a accommodation-convergence breakdown occurs due to the large disparity between the point at which the eyes of the user are focused, and the point at which the eyes of the user are converged. That is, the user's eyes focus on a plane of a screen and are simultaneously converged at a different 3D position, which is generated by disparity on the screen.
In addition, even when a portion of a displayed image has a depth that is outside a depth-of-focus (DOF) range of the user's eyes, the portion is clearly viewed. Consequently, a dual image created here causes eye fatigue.
Crosstalk occurs when the left image and the right image are not exactly divided in a stereo image system. That is, crosstalk occurs due to the incompletion of image switching in stereo glasses or the afterglow effect of a light-emitting device of a monitor. Further, even when the left image and the right image have been exactly divided, crosstalk may still exist because the degree of the division changes depending on a user's position.
When the display plane of a stereo image system is not perpendicular to the visual angle of a user, an image incident on both eyes of a user may be perceived as distorted.
The accommodation-convergence breakdown and crosstalk occur due to a horizontal error of the left image and the right image. Additionally, a vertical error or a rotation error of the left image and/or the right image may occur, also causing a user's eyes to become fatigued.
FIG. 1A illustrates a conventional stereo image including a vertical error, and shows that a vertical error 10a corresponding to “d” has occurred when arranging a graphics object 11a included in the left image, portion 1a, and a graphics object 12a included in the right image, portion 2a. 
As shown in FIG. 1A, graphics object 13a is included in the observed image shown in portion 3a, obtained by synthesizing the left image, portion 1a, with the right image, portion 2a. Accordingly, since the vertical error 10a corresponding to “d” exists in graphics object 13a, a user's eyes become fatigued.
FIG. 1B illustrates a conventional stereo image including a rotation error. FIG. 1B further shows that a rotation error 10b corresponding to “θ” has occurred when arranging a graphics object 11b included in the left image, portion 1b, and a graphics object 12b included in the right image, portion 2b. 
Accordingly, since the rotation error 10b corresponding to “e” exists in a graphics object 13b included in an observed image, portion 3b, obtained by synthesizing the left image, portion 1b, with the right image, portion 2b, a user's eyes become fatigued.
Korean Unexamined Patent No. 2005-0102156 discusses a technique where a disparity map including occlusion areas is formed by applying a disparity value of an input stereo image to a reference image, and each graphics object within the stereo image is divided by applying a predetermined threshold value to the disparity map compensated according to relative positions of graphics objects within the reference image, and a multi-view stereo image different from the stereo image is generated by differentially and horizontally shifting the graphics objects divided according to a horizontal parallax method.
However, the technique discussed in Korean Unexamined Patent No. 2005-0102156 only proposes generating a multi-view stereo image through horizontal shift of the left image and the right image, but does not avoid vertical and rotation errors.
Therefore, an apparatus, method and medium compensating for such vertical and rotation errors in displaying a stereo image has been found desirable by the inventors.